Fork - Dead at the top..

By RasmusDK, Posted June 3, 2012

2 month ago I changed the oil in my forks pumped all the air out and all, and set the oil level to 130mm. Since then the first 50mm or about 2 inch isnt damping.. Can that be fixed? I used putoline 2.5w oil..

By OUTLAWZRIDER83, Posted June 5, 2012

mine too whats with that

By RasmusDK, Posted June 5, 2012

Dont know yet, but it sucks in whoops and tight stuff. I have some oil from a friend, he got from some kinda suspension guru in holland that should be better. Ill keep you updated..

By grayracer513, Posted June 5, 2012

If you mean that the fork has rebound damping up until the last 50mm, then suddenly doesn't, that sounds like low oil level. Might try adding 10cc/side to see what happens. 2.5wt is kind of light for that old fork, too.

By RasmusDK, Posted June 5, 2012

Ive added new oil, not sure of the wt on this but its clearly higher. But still cant see its better.. Its like the seals are sticky or so.. btw i set the oil level to 130mm.

if I lift the wheel, pull the legs out and set a mark, set it back down and sit on it and lift the wheel up again, the legs arent coming all the way out, the upper 25mm of the legs isnt backing out again.. I hope you understand..

By grayracer513, Posted June 5, 2012

That's different. That sounds like a combination of friction and too little spring preload.

By RasmusDK, Posted June 5, 2012

Narh well the 50mm at the top still dont really do anything =) how do I add preload? Shims? Can you tell what the differences in oil level means/will do?

By grayracer513, Posted June 5, 2012

The higher the oil level, the less space there is for the captive air in the fork. The air acts as a part of the overall spring rate, and the smaller the air volume, the "stiffer" the air spring becomes. Lower oil levels ride nicer, but may bottom out more, and the fork is more likely to pull foam into the dampers, which makes them behave erratically. Higher oil levels help prevent bottoming and avoid foaming, but can cause a harsh overall feel.

By RasmusDK, Posted June 5, 2012

Ok thanks a lot! Makes sense.. How sensitive are these old forks to the oil level? Would it be stupid to add more then the 130mm ?

By VinceDC, Posted June 6, 2012

Set the oil level on that fork at 110mm.

By grayracer513, Posted June 6, 2012

Set the oil level on that fork at 110mm.

When I had my '03 (same fork), I used to run the oil at 110-115. That seemed to be the best for my purposes. Later I added sub tanks and was able to run it higher, and that helped with plushness and with fading on long rides.

By RasmusDK, Posted June 6, 2012

Will try, thanks. Do you know how many cc to 5 mm for example?

By grayracer513, Posted June 6, 2012

No, unfortunately. It varies quite a bit based on what point the oil level is at when more is added. The volume where the top 5mm of oil may go can be partly filled by the springs and other internals, so it's about impossible to calculate.

By RasmusDK, Posted June 6, 2012

Roger. When i set the level yesterday it was about 30 mm to high, and i sucked about 30 ml out so ill just try and add 10 ml..

By VinceDC, Posted June 7, 2012

With that fork to set the oil level and have it be reliable you need to lift the outer tube all the way up then down to get the oil out of the space between the tubes. Then set the level.If you don't do this you can see as much as a 25-30mm difference.

Edited June 7, 2012 by VinceDC

By RasmusDK, Posted June 7, 2012

Nothing helped, guess this old fork is just worn out..

By grayracer513, Posted June 7, 2012

With that fork to set the oil level and have it be reliable you need to lift the outer tube all the way up then down to get the oil out of the space between the tubes. Then set the level.If you don't do this you can see as much as a 25-30mm difference.

In fact, Yamaha specifically recommends against doing what you suggest. The manual clearly states that the fork should be filled, then the air pumped out of the damper (adding oil as necessary if the top of the damper becomes exposed), and then to work the outer tubes up and down no more than 200mm (~8") from the compressed position. Raising the outer tube more than that will spill oil into the center that should not be there, and won't be there later on once the fork is put into operation, and will likely result in the oil level being too low.

By RasmusDK, Posted June 7, 2012

In fact, Yamaha specifically recommends against doing what you suggest. The manual clearly states that the fork should be filled, then the air pumped out of the damper (adding oil as necessary if the top of the damper becomes exposed), and then to work the outer tubes up and down no more than 200mm (~8") from the compressed position. Raising the outer tube more than that will spill oil into the center that should not be there, and won't be there later on once the fork is put into operation, and will likely result in the oil level being too low.

Saw or heard that you shouldnt do that too somewhere, but never knew why not to..

I was out in some sand whoops today I drove there for 30 min or so, and after the 30 min with the "air spring" fact in mind that you told grey, I tried to push my little after marked fork air drain valves, but there was no pressure in any of the legs.. Now thats not right is it?

By grayracer513, Posted June 7, 2012

I was out in some sand whoops today I drove there for 30 min or so, and after the 30 min with the "air spring" fact in mind that you told grey, I tried to push my little after marked fork air drain valves, but there was no pressure in any of the legs.. Now thats not right is it?

Does seem a little odd. But if there are no visible leaks, then there's not much to worry about.

By VinceDC, Posted June 8, 2012

Someone should call Race Tech and Jeff Slavens and tell them there wrong?